Nitrogen and oxygen in steel smelting applications
Widely used in metal heat treatment, powder metallurgy, magnetic
materials, copper processing, wire mesh, galvanized wire,
semiconductor, powder reduction and other fields. Its advantages
are: fast, high yield, high quality, many varieties and low
investment. Therefore, oxygen blowing method is widely used
in steelmaking such as smoke blown converter, open
hearth furnace and electric furnace.
Ultra Low CO2 Steelmaking - ULCOS
For more than 25 years， the steel industry around the world has identified climate change as a major environmental challenge. Long before the conclusions of the Intergovernmental Panel on Climate Change (IPCC) in 2007， major steel producers recognized that long-term solutions were needed to address carbon dioxide (CO2) emissions from steel production processes.
As a result， the steel industry has been very proactive in improving energy consumption and reducing greenhouse gas (GHG) emissions.
The GHG most relevant to the world steel industry is carbon dioxide (CO2). According to the World Steel Association (WSA)， an average of 1.8 tons of CO2 gas is emitted for every ton of steel produced. According to the International Energy Agency (IEA)， the steel industry accounted for about 6.7% of the world's total CO2 emissions in 2010.
Now， CO2 emissions are about 50% lower per ton of crude steel， which makes the steel industry's climate impact much lower. High-quality steel mills are now operating close to the thermodynamic limits set by current steel production technology. This， in turn， means that steel producers are limited in further improving energy efficiency. Since most of the major energy savings have already been achieved， it is unlikely that any further significant reductions in CO2 emissions will be possible using current technology.
Further reductions in greenhouse gas emissions mean the introduction of breakthrough technologies. Reducing CO2 emissions to the levels required by post-Kyoto policies requires "out-of-the-box" thinking， as it presents specific challenges. There are no off-the-shelf， simple processes that can be used to achieve this goal. A deep paradigm shift in the way steel is produced must be imagined， and corresponding breakthrough technologies must be designed and developed. The kind of reductions demanded by governments and international agencies require the invention and implementation of radically new production technologies.
This is the background for the creation of the ULCOS (Ultra Low CO2 Steelmaking) program， a European collaborative research and development initiative launched in 2004 as a result of the Kyoto Protocol. ULCOS seeks ways to further significantly reduce CO2 emissions from steel production. The main goal of the program is to find breakthrough process lines that， when fully developed in the future， can demonstrate the potential for significant reductions in CO2 emissions in iron ore-based steel production. The program's goal is to reduce CO2 emissions by at least 50% compared to today's production technologies. Achieving such an ambitious goal will require a paradigm shift in steel production that will change the way steel mills around the world currently operate. ulcos is part of a global steel industry program to identify steelmaking technologies that have the potential to achieve significant CO2 reductions. Under the program， people are trying to find an answer to making steel in the most sustainable way possible.
The ULCOS program is made up of a consortium of 48 European companies and organizations from 15 European countries， including all major European Union (EU) steel companies， energy and engineering partners， research institutes and universities. It is also supported by the European Commission. ULCOS is a European project， but it is a professional effort in the worldwide steel industry that actively seeks to address the threat of global warming. The consortium's expertise ranges from steelmaking to biomass production and geological storage of CO2， and includes process engineering， energy economics and forward-looking research on climate change.
Today， ULCOS is a professional initiative within the global steel industry that actively seeks solutions to the threat of global warming. ULCOS partners contribute 60% of the €75 million budget. The European Commission provides the remaining 40% through its RTD (Research and Technology Development) framework program and the RFCS (Research Fund for Coal and Steel) program. Both were established to promote industrial research and technological development within Europe.
Current steel production technologies are based on coal， which is mainly carbon， on a mixture of natural gas based on carbon and hydrogen， and on waste-based electric arc furnaces. In order to define a clean process route for CO2， three main possible paths for solutions are (i) a shift from coal， called decarbonization， where carbon would be replaced by hydrogen or electricity in processes such as hydrogen reduction or electrolysis of iron ore， (ii) the introduction of CCS (carbon capture and storage) and mineral carbonization technologies， and (iii) the use of sustainable biomass.
ULCOS is a large scale program carefully set up to address the long term and complex challenges facing the steel industry and society as a whole. the ULCOS program has four steps， namely (i) establishment of process concepts， (ii) large scale demonstration， and (iii) large scale experimentation in the first commercial plant. (iv) deployment of the technology in Europe and worldwide. ULCOS is a research program that has been transformed into a demonstration program.
Since its inception in 2004， the ULCOS program has conducted a significant amount of research. In the initial phase of its research program， a preliminary feasibility study lasting four to five years investigated more than 80 technologies/concept lines， using modeling and laboratory methods to assess their potential in terms of CO2 emissions， energy consumption， operating costs and sustainability of steelmaking. Several concepts have been investigated in parallel. Of all these concepts， most of the following process route families have been selected in the ULCOS program for further investigation and eventual scale-up to a scale that would allow commercial implementation
A variant of the blast furnace (BF) in which the top gas of the blast furnace undergoes carbon dioxide capture and the remaining reducing gas is reinjected into the bottom of the reactor and is operated with pure oxygen rather than hot air (air). This process is called Top Gas Recirculation Blast Furnace (TGR-BF). The CO2-rich gas stream is fed into storage (CCS technology).
A smelting reduction process known as the HIsarna process. This process is based on a combination of a hot cyclone furnace and a melting bath and contains some of the technical features of the HIsmelt process. The process also uses pure oxygen and produces an exhaust gas that can be used almost exclusively for storage (CCS technology).
A direct reduction (DR) process， known as ULCORED， produces DRI (direct reduced iron) in a shaft furnace， either using natural gas or gas produced by coal gasification. The waste gas from the shaft furnace is recovered into the process after capturing carbon dioxide， which leaves the DR plant as a concentrated stream and is stored (CCS technology).
Two variants of the electrolysis process are known as ULCOWIN and ULCOLYSIS. ULCOWIN operates in an aqueous alkaline solution with small grains of ore at slightly above 100 degrees C (electrolysis process). ULCOLYSIS operates at steelmaking temperatures with a molten salt electrolyte made from slag (thermal electrolysis).
There are also two alternative options available. The first one is a direct reduction using hydrogen， which does not generate any carbon emissions， if any. The second is based on the use of sustainable biomass， the first being charcoal produced from sustainable plantations of eucalyptus trees grown in tropical countries.
Among the new ultra-low carbon technologies， the use of CCS and mineral carbonation has also been evaluated.CCS has been considered a powerful solution from the beginning. With respect to mineral carbonation， it has been determined that it can only lead to modest， albeit significant， overall reductions in emissions.
Figure 1 shows the processes being researched and developed under the ULCOS program.
Figure 1 Processes being researched and developed under the ULCOS program
ULCOS has now selected four process concepts - which have been experimentally tested - that can reduce CO2 emissions by more than half compared to current best practices. These concepts are now being implemented in working steel mills in the second phase of the ULCOS project. the results of the second phase of the ULCOS project are likely to be rolled out to production plants in about 15 to 20 years. The process concepts chosen are (i) redesign of the blast furnace to incorporate CCS into the core of the process， (ii) smelting reduction with CCS capability， (iii) extensive use of natural gas with cleaner CO2 technology than today， and (iv) hydrogen steelmaking and electrolysis of iron ore.
In the short term， TGR-BF seems to be the most promising solution， as existing BF can be adapted to the new technology. This could allow for some control of the large capital expenditures required to move to breakthrough technologies. In addition， the principle of the process can save energy because the capture of CO2 and recovery of purge gas replaces the high temperature chemical equilibrium (Boudua reaction)， and the use of coke and coal within the BF is more efficient than in conventional operations. This balances to some extent the additional costs incurred for capture and storage. The right concept to apply to TGR-BF is the CO2 capture in the process， as well as the oxygen operation. The oxygen part is similar to the oxyfuel operation， but not identical. The recirculation part is original and is the key reason to get some energy savings and a corresponding cut in operating costs. The concept has been tested on a large laboratory blast furnace in Lule?， Sweden， and the results have been positive.
Where natural gas is available， the ULCORED process route is an attractive option. The concept applied to the ULCORED process is similar to the TGR-BF concept， which also includes in-process recovery using pure oxygen and furnace top gas， in addition to other features such as a series of shift reactors in the recovery cycle. To validate the concept， ULCOS' partner LKAB plans to set up a one-ton per hour pilot in Lule? in the next few years.
The HIsarna process， which is under development， will be an available option for the Greenfield steel plant in the next few years. the HIsarna process is slightly different from the TGR-BF and ULCORED processes because it does not involve a recovery cycle for the gas. The smelter gas is oxidized at the cyclone level where some reduction takes place while combustion takes place to preheat and melt the ore. The gas has a countercurrent to the iron stream in which its chemical energy is completely depleted. A pilot plant of 8 t/h has been set up and tested during the course of the ULCOS project. The pilot plant was launched in April 2011. In the first campaign， the plant was operated from April 18 to June 11， 2011. There were four start-ups. The first start-up was not successful. The other three start-ups were successful. The achieved injection rate was 60% of capacity. The available operating data indicates that the process is operating as expected， but more operating time is needed to confirm this. Operating hours are lower than expected. The second campaign has started on October 16， 2012. It continued until the end of November 2012.
The electrolysis processes were developed from scratch within the ULCOS program and， therefore， are still operating at laboratory scale. Although they hold the promise of zero emissions， it will take time to scale them up to commercial scale (10 to 20 years) if green power is available. The ULCOWIN process includes alkaline electrolysis of iron ore. Electrolysis is typically used to produce metals other than steel and requires large amounts of electricity. The process will depend on clean power sources for CO2， such as hydro or nuclear power. ulcolysis is molten oxide electrolysis. Molten oxide electrolysis works by passing an electric current through a molten slag containing iron oxide. The iron oxide decomposes into liquid iron and oxygen. No carbon dioxide is produced. Process emissions can be further reduced by using a clean power source of carbon dioxide.
In hydrogen steelmaking， the iron is reduced from the iron ore at high temperatures (above 1300 degrees Celsius) and the reaction time is very short. There are no CO2 emissions， but the production of hydrogen requires large amounts of CO2 clean electricity. The process can also be operated with low CO2 fuels such as natural gas.
Hydrogen steelmaking depends heavily on the availability of green hydrogen， while the use of charcoal far from the growing countries requires the establishment of complex logistics， including heavy infrastructure across several continents.
ULCOS is a long-term initiative for the steel industry. It is full of promise， but it also has risks and pitfalls， a situation that may be similar to what other industries are experiencing. The risks are related to the complexity of the problem， which requires the development and implementation of breakthrough technologies in a very short period of time. It will take patience， support， sincerity and continued commitment to make this program a successful initiative for the steel industry and to achieve most of its goals.
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